looking for data on maize plantations in rift valley

Thinking of what to do in the virtual kenya competition

am looking for the following datasets, soil data, rainfall data, elevation data, population data, agricultural data , all for meru district for the following years, 1970,1980,1990,2000,2010 or even the latest, i need them for a simulation project that am doing, anybody who can assist
will be highly appreciated.

The results of the 2010 Referendum as viewed on Google maps.....part of my final year project http://kenyaelectionmaps.blogspot.com/2012/04/sample-code.html